So a few months back, Plushie noticed that her comments were apparently getting eaten by the site; no error message, no confirmation, no sign of the comment after submitting - nothing.
The mystery persisted for a while and I just couldn't get to the bottom of it despite a couple hours' worth of investigation and testing, so I shelved it. Just a few days ago, we were reminded of the issue when she tried commenting and once again, had it unceremoniously raptured into the ether.
To cut a long story short, after I looked in the right places I learned that several other people's comments were being similarly filtered out and tossed in the bin without any indication. The culprit?
WordPress' default moderation filter blocks users with .biz, .cn, .info, hotmail and yahoo email accounts from commenting.
... Well, that's thankfully fixed now. Apologies to those affected, but your comments have since been rescued and restored!